I. Field of the Invention
The present invention relates generally to mobile wireless terminals, and particularly, to mobile wireless terminals having multiple modems which are constrained to operate under an aggregate transmit power limit for all of the modems.
II. Related Art
In a data call established between a mobile wireless terminal (MWT) and a remote station, the MWT can transmit data to the remote station over a “reverse” communication link. Also, the MWT can receive data from the remote station over a “forward” communication link. There is an ever pressing need to increase the transmit and receive bandwidth, that is, the data rates, available over both the forward and reverse links.
Typically, the MWT includes a transmit power amplifier to power-amplify a radio frequency (RF) input signal. The power amplifier produces an amplified, RF output signal having an output power responsive to the input power of the input signal. An inordinately high input power may over-drive the power amplifier, and thus cause the output power to exceed an acceptable operating transmit power limit of the power amplifier. In turn, this may cause undesired distortion of the RF output signal, including unacceptable out-of-band RF emissions.
Therefore, there is a need to carefully control the input and/or output power of the transmit power amplifier in an MWT so as to avoid over-driving the power amplifier. There is a related need to control the output power as just mentioned, while minimizing to the extent possible, any reduction of the forward and reverse link bandwidth (that is, data rates).